Evaluating the effectiveness and longevity of grounding bearings in mitigating EDM bearing currents in electric machines and drive systems

In order to mitigate the occurrence of EDM bearing currents in electric drive systems, a variety of shaft-grounding systems can be employed. However, their effectiveness and longevity are not guaranteed, as they are significantly influenced by operating conditions and environmental factors. This article introduces two metrological investigations concerning the use of grounding bearings. To begin, the study presents a theoretical review of shaft-grounding systems and the fundamental functionality of grounding bearings in particular. The first investigation, which focuses on measurements conducted on a real drive system, is subsequently described. In this setup, a small grounding bearing is integrated into a traction motor. The bearing current peak amplitudes, the bearing voltage, and the resulting apparent bearing power are then compared with the unmodified state. Later, the second investigation is presented, which involves long-term testing of grounding bearings on a shaft-grounding test bench, with emphasis on ageing effects and longevity.